LoveExample-18 向指定的位置发射子弹

    Long time no see~ 虽然可能本来看的人也不多吧 示例在视觉上其实很朴素,不过实现了定点射击的功能,这个功能感觉还是比较常用的。 大概思路就是,在 update 方法中,不断将获取到的鼠标位置(如果点击了话)放到表中,同时又不断的从表中取出存放的子弹信息进行绘制。 逻辑上并不难,但是有些 lua 语言本身的点。 代码如下:

    function love.load()	
    	SPEED = 250
    	StartPos = {x=250, y=250, width=50, height=50}	--The starting point that the bullets are fired from, acts like the shooter.
    	bullets={}										--The table that contains all bullets.
    function love.draw()
    	--Sets the color to red and draws the "bullets"., 0, 0)
    	--This loops the whole table to get every bullet. Consider v being the bullet.
    	for i,v in pairs(bullets) do"fill", v.x, v.y, 4,4)
    	--Sets the color to white and draws the "player" and writes instructions., 255, 255)
"Left click to fire towards the mouse.", 50, 50)"line", StartPos.x, StartPos.y, StartPos.width, StartPos.height)
    function love.update(dt)
    	if love.mouse.isDown(1) then
    		--Sets the starting position of the bullet, this code makes the bullets start in the middle of the player.
    		local startX = StartPos.x + StartPos.width / 2
    		local startY = StartPos.y + StartPos.height / 2
    		local targetX, targetY = love.mouse.getPosition()
    		--Basic maths and physics, calculates the angle so the code can calculate deltaX and deltaY later.
    		local angle = math.atan2((targetY - startY), (targetX - startX))
    		--Creates a new bullet and appends it to the table we created earlier.
    	for i,v in pairs(bullets) do
    		local Dx = SPEED * math.cos(v.angle)		--Physics: deltaX is the change in the x direction.
    		local Dy = SPEED * math.sin(v.angle)
    		v.x = v.x + (Dx * dt)
    		v.y = v.y + (Dy * dt)
    		--Cleanup code, removes bullets that exceeded the boundries:
    		if v.x > or
    		   v.y > or
    		   v.x < 0 or
    		   v.y < 0 then
    • for i,v in pairs(bullets) do … end 这个循环体的意思是,遍历 bullets 中的信息,i 为键,v 为值,对每个键值对进行相应的操作。 lua 的循环写法颇有个性,详情可在在线教程上看。
    • table.insert(bullets,newbullet) table 是 lua 中的一个常用数据结构(那位大神的代码里,table 随处可见) 该方法意思是,将 newbullet 放入到 bullets 中。